The present invention relates to a new and improved method and apparatus for fault and/or fault direction detection.
Generally speaking, the method and apparatus for the fault and/or fault direction detection at electrical lines contemplates forming current surge or jump signals and voltage surge or jump signals in accordance with the changes as a function of time of the line current and line voltage, respectively, in relation to the steady-state current and voltage course. The formed current surge and voltage surge signals experience a threshold value comparison and, if desired, a sign comparison.
A method of this type and, equally, equipment for the performance thereof, have become known to the art from German Patent Publication No. 2,353,424 and the corresponding U.S. Pat. No. 3,878,460. That prior art teaching contemplates subjecting a current and a voltage surge signal, caused by a fault or a load exchange, to a sign comparison and each for itself to a threshold or limit value comparison. An equality or inequality of the signs, as the case may be, in an indicia for a reverse direction of forward direction of the fault or load change, whereas a conjunctive logical coupling of both surge or jump signals exceeding the threshold value can be employed as prerequisite for tripping. In consideration of the trip sensitivity such method is comparatively markedly dependent upon the impedance at the reverse side of the measuring location (source impedance) and exhibits low security against faulty tripping.